The dynamics of this FFL can be described as follows: when p53 begins to accumulate as a response to stress signals MDM2 first rises since it is positively regulated by this gene. miR-34a is one of the direct target genes of p53, thus, at some level of p53 the expression of miR-34a begins also to increase, when it reaches some cellular level MDM2 begins to decrease. It has been demonstrated that the response time of the type 1 incoherent FFL is smaller than the one of a single regulation system [1]}.
